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Prosecutors now say suspected serial killer Rex Heuermann kept meticulous notes on how to kill and get away with it as his alleged methodology changed over the course of nearly two decades and at least six murders he is accused of committing.

A deleted document investigators say they recovered from his computer shows he noted how many traffic cameras he would pass on his way to the dump sites, how to "prep" a victim's body for disposal and a reminder to use push-pins to hang a drop cloth, Dexter Morgan style, rather than tape.

Although investigators now say the suspected killer evolved over the years, many of the victims were discovered wrapped in some kind of material, whether it be a hunter's camouflage burlap or a surgical drape.

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Despite his alleged efforts to scrub away evidence of his own DNA and fingerprints, prosecutors have alleged that hairs found on multiple victims belonged to either Heuermann or members of his household.

His family has not been accused of assisting in any of the crimes – they were out of town during each murder, according to court documents.

Read Exhibit B, the HK2002-04 file:

In a statement released by her attorney, his estranged wife Asa Ellerup said she does not believe Heuermann is capable of committing the crimes and that she was unaware of his activities, if what prosecutors allege is true.

"Today's Indictment further illustrates that, Asa Ellerup has no involvement in any of the alleged crimes that her estranged Husband, Rex Heuermann, has been charged with," said her lawyer, Bob Macedonio. "Ms. Ellerup married Rex Heuermann in 1996. She was not residing with Rex Heuermann in the Massapequa Park domicile in 1993, the year Ms. Costilla was murdered. Moreover, according to the Government, at the time of the death of Ms. Taylor, Ms. Ellerup was, once again, not in the jurisdiction."

According to the filings, police have now received reports of Heuermann's old Chevy Avalanche from two witnesses in connection with two separate murders. They have decades of phone records and internet searches. They have his DNA.

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And they have meticulous notes in a computer file called "HK2002-04," which Heuermann allegedly deleted from a computer – but not fully. Forensic investigators found it.

The file has lists of "problems," "supplies," dump sites and targets. It has checklists for "pre-prep," "prep" and "post event." There are notes including page numbers from FBI profiler John Douglas' groundbreaking book, Mindhunter. And the number of traffic cameras along two highways between Heuermann's home in Massapequa Park and the dump sites in Manorville and North Sea are listed.

A section on "things to remember" notes that sound travels, killing without proper sleep "creats (sic) problem," and "hit harder." 

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"Use push pins to hang drop clothes from ceiling – not tape," it reads. And light rope breaks too easily "under stress of being tightened" – use the heavy kind.

A section on "body prep," contains gruesome, step-by-step instructions for disposing of the victims, including "wash body inside and all cavities" and "remove trace evendice (sic) [finger prints/hair]." 

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If the allegations prove true, he failed.

"There are so many smoking guns this looks like a battlefield," said Joseph Giacalone, a retired NYPD sergeant and a cold case expert at John Jay College of Criminal justice. "The issue that it comes down to is the evidence in these cases now, as well as the Gilgo Four, in my opinion, is insurmountable."

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He said he believes prosecutors may have already offered the suspect a plea deal in exchange for full information on the scope of the crimes.

"At this point, what is the defense going to be? Are you going to try to attack the new technology? Good luck with that. Are you going to try to attack hair [found] at the scene? And his wife’s hair? Good luck," he said.

"We don’t even know if there are any photos of this either," he added.

In the document prosecutors allege they recovered from Heuermann's computer, one of the items listed under "supplies" was "photo film."

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Heuermann was arraigned on two new murder charges Thursday in the deaths of Jessica Taylor in July 2003 and Sandra Costilla in November 1993. They were both tortured and brutalized – with Costilla suffering 25 post-mortem stab wounds, according to prosecutors. Taylor was dismembered, with body parts dumped in two locations.

John Kelly, a criminal profiler and the founder of STALK Inc., said serial killers typically evolve over time, especially if they are active for many years.

"When they start they start to experiment with different methods of killing until they find their method of choice," he told Fox News Digital. "The same with this guy's torture of choice, he experimented, until he found the one that gave him sexual excitement and satisfied his fantasy."

The Gilgo Four victims were all found under similar circumstances to one another. Dramatic differences in the Taylor and Costilla cases could lead investigators to investigate Heuermann in connection with a number of unsolved murders that didn't match the original methodology, he said.

Police arrested the 59-year-old New York City architect last year in connection with three cold case murders and prosecutors secured an indictment for a fourth victim months later. He made a brief appearance in court Thursday in a suit and handcuffs, and is due back on July 30.

In July 2023, police arrested Heuermann outside his Manhattan office and spent nearly two weeks scouring through his home in Massapequa Park, about 20 minutes from where police found the bodies of Melissa Barthelemy, 24; Megan Waterman, 22; and Amber Costello, 27, in 2010.

Prosecutors later tacked on charges for the murder of Maureen Brainard-Barnes, 25, whose remains they found near the others.

The prime suspect in Costilla's death was previously another serial killer, former Manorville carpenter John Bittrolff, who is currently in prison for two other murders.

Suffolk County District Attorney Ray Tierney, the lead prosecutor on the case, told reporters Thursday that investigators were still examining hundreds of electronic devices seized last year from Heuermann's home. 

Heuermann has pleaded not guilty in all six murders. His trial is expected to be further delayed as a result of the new indictment.

Cold case investigators in New York and at least three other states are looking into his potential connection to additional homicides.

"I think when all is said and done, we're gonna find out that Rex is one of the most prolific serial killers we've ever seen," Giacalone predicted. "This opens up dozens, if not scores of available victims for Rex from 1993 or even before, because it still puts him at the 31 years of age mark, which is still pretty old compared to some of the other killers we’ve seen. And we have that huge gap between 2011 and his arrest in 2023."